Recently, there is extensively utilized an endoscope (called also a scope or fiber scope) whereby, by inserting an elongate insertable part into a body cavity, organs within the body cavity can be observed or, as required, by using a treating tool inserted through a treating tool channel, various therapeutic treatments can be made.
Also, there are suggested various electronic scopes wherein such solid state imaging device as a charge coupled device (CCD) is used for an imaging means.
In the color picture image imaging system of such electronic scope, there are such frame sequential type wherein an illuminating light is sequentially switched to R (red), G (green) and B (blue) as is shown, for example in the publication Of Japanese Patent Application Laid Open No. 82731/1986 and such color mosaic type (called also a simultaneous type) wherein a filter array in which color transmitting filters transmitting respectively color lights of R, G and B are arrayed is provided on the front surface of a solid state imaging device as is shown in the publication of Japanese Patent Application Laid Open No. 76888/1985.
Now, in the frame sequential type electronic scope, as the illuminating light illuminating an object is transmitted through color separating filters of R (red), G (green) and B (blue) to be separated into the respective colors, the illuminating light amount will reduce to be lower than in the color mosaic type radiating a white light to the object and, in the case of confirming the tip position of the electronic scope by the transmitted light outside the body, the illuminating light amount will be so small as to make it hard to confirm the tip position. In order to solve this problem, as shown, for example, in the publication of Japanese Patent Application Laid Open No. 2927/1982, there is disclosed a technique of increasing the light amount by removing the color separating filters from the light path even when the frame sequential type electronic scope is used. However, the monitor image in this case will be neither an intrinsic color picture image nor a black and white picture image while the color separating filters are moved out of the light path from within the light path or, on the contrary, into the light path from outside the light path. Further, by the movement of the organ within the body, a so-called color smear will be produced in the picture image. There have been such problems.
On the other hand, in the mosaic type electronic scope, in case the position of the tip part is hard to recognize, the light amount of the light source apparatus may be increased but, when it is increased, as the primary color signals of R and B are superimposed as modulated carrier signals on the color signal G or luminance signal Y, the output signal of the solid state imaging device will quickly saturate the color signal components and, as a result, will produce a skipped color picture image very hard to see as an observed picture image.